Various kinds of active and passive RF and microwave filters are used in telecommunications devices to reject out-of-band signals, filter undesired harmonics and spurious components from signals prior to transmission and for performing various other functions within the telecommunications devices.
In particular, a Group Switched Mobile (GSM) filter may be required in the output of the transmitter for GSM transceivers and a Digital Cellular System (DCS) filter may be required in the output of the transmitter for DCS transceivers. Both are typically required for a dual-mode telecommunications transceiver. Similar filters may also be needed in wireless local area network (WLAN) and wireless personal area network (WPAN) devices, such as Bluetooth and 802.11 devices, for e.g. attenuation of the second harmonic of the signal source. The above-mentioned filters occupy a significant amount of circuit board area and package volume within the transceiver.